1. Field of the Invention
This invention relates to a portable camera employing a consumable photosensitive recording medium and electrostatographic techniques in the preparation of line copy and/or reproduction having extended dynamic range. Image formation and development take place within the camera. The fixation of the developed image is achieved either within or outside the camera by overcoating the developed image on the recording surface of the photosensitive medium with a permanent supporting film or paper base followed by delamination of the recording layer of the photosensitive medium from the other components of said medium.
2. Description of the Prior Art
The formation and development of images on imaging layers of photoconductive materials by electrostatic means is well known. The best known of the commercial processes, more commonly known as xerography, involves forming a latent electrostatic image on the imaging layer of an imaging member by first uniformly electrostatically charging the surface of the imaging layer in the dark and then exposing this electrostatically charged surface to a light and shadow image. The light-struck areas of the imaging layer are, thus, rendered relatively conductive and the electrostatic charge selectively dissipated in these irradiated areas. After the photoconductor is exposed, the latent electrostatic image is rendered visible by development with finely divided colored electroscopic materials, known in the art as "toner". This toner will be principally attracted to those areas of the image-bearing surface, which retain the electrostatic charge and thus, form a visible powder image. The developed image can then be affixed to the photoreceptor (where the recording surface differs in color from the toner) or it can be transferred to a receiving member (preferably a sheet of untreated paper) and subsequently affixed thereto by solvent or thermal fusion techniques. Alternative methods of developed image fixation include overcoating of the developed image with transparent films or coatings or lamination of the recording surface to a permanent support film or paper, followed by stripping the recording surface from the photoreceptor structure.
The methods used in sensitization of the imaging surface of an imaging layer in electrophotography have been many and varied. In order to achieve acceptable copy quality, it is essential that the imaging layer be uniformly charged and that the magnitude of the charge be sufficient to enable formation of a latent image having sufficient conrast potential to be capable of development with electrophotographic developer materials. The most widely accepted technique for achieving this result is sensitization by one or more corona electrodes. Corona sensitization generally involves maintaining the corona electrode(s) at a potential of about 7000 volts (relative to ground) while simultaneously passing the photoconductor in close proximity to the electrode. The ionization of the air in the immediate vicinity of the corona electrode results in a cascade of charged air molecules onto the surface of the imaging layer of the photoconductor thereby imparting the desired degree of sensitization. The configuration of the electrode, its rate of travel and distance relative to the photoconductive insulating layer of the imaging member, must be carefully controlled in order to insure uniformity of potential and regularity in distribution of the surface charge. Slight surface irregularities in the photoconductive insulating layer do not adversely affect the ability of this type of charging system to uniformly blanket the imaging surface with a sensitizing charge, since the lands and valleys of the photoconductive insulating layer are equally accessible to the charged air molecules.
As is readily apparent, corona sensitization is not readily adaptble to a portable electrostatographic reproduction system insofar as the energy and voltage requirements of such a system far exceed that which is attainable where the source of energy is a battery.
One proposed alternative to corona sensitization is contact charging the surface of the photoreceptor by means of establishment of a physical junction between a source of electrical potential and the surface of the photoconductive insulating layer. This physical junction can be a biased roller or slightly conductive solution containing an electrolyte. Contact charging with biased rollers generally does not provide the imaging surface with a potential of sufficient magnitude to produce an acceptable, developable latent image. The principal reason for the inability of such contact charging to prove satisfactory is the inability to establish a sufficient number of point contacts between the biased roller and the surface of the photoconductive insulating layer.
Where the physical junction between the source of electrical potential and the imaging surface of the imaging layer is a low conductivity liquid (or an insulating liquid containing an electrolyte), sufficient point contact is no longer a problem since the entire photoreceptor surface is "wetted" with the charge carrying medium. Such liquid charging systems are, however, beset with the number of problems which are inherent in the use of liquids. For example, losses of the fluid by evaporation or by spilling are recurrent disadvantages. Furthermore, in the event that some electrolyte is lost from the charge-transfer medium by virtue of being transferred to the copy sheet or some other imbalance established within the solution, the conductivity of liquid will change and, thus, its ability to repeatedly impart the desired degree of sensitization. Both of the contact-charging systems described above do possess one inherent advantage over corona sensitization in that the power demands of these contact charging systems are substantially less.
Accordingly, it is the object of this invention to provide a portable reproduction system, which is compatible with electrophotographic imaging and development and fixing techniques.
More specifically, it is the primary object of this invention to provide a portable, electrophotographic camera wherein the photosensitive member can be uniformly sensitized by essentially liquid-free, contact charging techniques.
Another object of this invention is to provide a portable, electrophotographic camera wherein the photosensitive member comprises an overcoated panchromatic photoconductive composition.
Still another object of this invention is to provide a portable, electrophotographic camera wherein the latent image is developed within the camera with standard electrophotographic developer compositions.
Additional objects of this invention include the provision of an imaging method for utilization of the above camera and the reproduction created thereby.